<define/Child|input|>
  <const/{ a, b } = input>
  <div>${a}</div>
  <div>${b}</div>
  <script>if (a !== "a") throw new Error("did not serialize a")</>
  <script>if (input.a !== "a") throw new Error("did not serialize input.a")</>
</>
<Child a=input.a b=input.b/>